The present invention relates to mixtures of periclase and carbonaceous materials, and especially to such mixtures formed into bricks.
Periclase (magnesium oxide or magnesia) bricks are a form of refractory brick used in steel making, foundry operations and particularly in basic oxygen furnaces, where exposure to a basic slag is encountered. Such bricks are made by mixing a major proportion of magnesium oxide granules of defined particle size distribution, a carbonaceous binding material capable of undergoing pyrolytic decomposition (e.g. pitch of a defined softening point) and, usually, a graphitic granular carbon material such as various forms of carbon black. After mixing, the formulation is compressed under extremely high pressures (e.g. greater than 5,000 pounds per square inch or 34.5 MPa, preferably greater than 10,000 pounds per square inch or 69 MPa), at a controlled temperature (e.g. 175.degree.-190.degree. C.). The resultant "green" brick has a density of at least about 180 pounds per cubic foot (2.9 g/cm.sup.3 or 2,880 kg/m.sup.3). Thereafter, the green brick is annealed or tempered at temperatures such as 260.degree.-320.degree. C. to form the final brick which is used in the furnace. During exposure to the much hotter temperatures present in the furnace, the carbonaceous binding material is coked.
It is known that the properties, and especially the useful life, of the product brick correlates strongly with green brick density. Therefore a variety of techniques, including increased pressure and optimized compression temperature, have been employed to increase this value.